Reconfigurable terminal

Abstract

A device is provided for use in, e.g., XO and VCXO applications that utilizes a terminal that can function in a first mode as a serial communications port and in a second mode as an output enable terminal controlling, for example, the clock output(s). In the first mode, the output enable function is unavailable through the terminal. After the terminal is programmed to operate in the second mode, the terminal functions permanently in the second mode.

1 . An apparatus comprising: 
 a terminal;    control circuitry coupled to the terminal to permanently convert the terminal from a first mode of operation in which serial communications are received over the terminal into a second mode of operation in which the terminal functions to selectively enable an output according to a voltage value on the terminal.    
   
   
       2 . The apparatus as recited in  claim 1  wherein once the terminal is converted to the second mode of operation the terminal function cannot be converted into the first dedicated mode of operations.  
   
   
       3 . The apparatus as recited in  claim 1 , wherein a terminal configuration determining the mode of operation of the terminal is stored in a non-volatile memory.  
   
   
       4 . The apparatus as recited in  claim 1  wherein the control circuit is responsive to a communication received over the terminal to convert terminal to the second mode of operation.  
   
   
       5 . The apparatus as recited in  claim 4  wherein the serial communication received over the terminal in the first mode of operation includes a command and write data.  
   
   
       6 . The apparatus as recited in  claim 1 , wherein the control logic distinguishes between a calibration clock received on the terminal and serial communications when in the first dedicated mode of operation.  
   
   
       7 . The apparatus as recited in  claim 1  wherein the output enable function is for controlling the output of one or more clocks.  
   
   
       8 . The apparatus as recited in  claim 6  further comprising: 
 a controllable oscillator coupled to receive a reference frequency and to supply a clock signal that is coupled to an output terminal that is controlled by the terminal functioning to selectively enable the output according to the voltage value on the terminal; and    a resonating device coupled to supply the reference frequency.    
   
   
       9 . The apparatus as recited in  claim 8  wherein the terminal is on a package, the package including an integrated circuit and a resonating device, the integrated circuit including the controllable oscillator, and the resonating device being one of a crystal and surface acoustic wave (SAW) device.  
   
   
       10 . The apparatus as recited in  claim 1  further comprising a second terminal that functions as a dedicated programmable input/output terminal over which serial communications and a calibration clock are received, the second terminal not being convertible into a dedicated input control for an output enable function.  
   
   
       11 . A method comprising: 
 utilizing a terminal in a first mode of operation in which serial communications are received over the terminal and; and    subsequently converting the terminal to a second mode of operation in response to a received command, in which the terminal functions as the input control for selectively enabling an output according to a value of terminal voltage.    
   
   
       12 . The method as recited in  claim 11  wherein the conversion to the second mode of operation is permanent.  
   
   
       13 . The method as recited in  claim 11 , further comprising storing a terminal configuration selecting one of the first and second modes of operation in a non-volatile memory.  
   
   
       14 . The method as recited in  claim 11  further comprising converting the terminal from the first mode to the second mode of operation in response to the command being received over the terminal.  
   
   
       15 . The method as recited in  claim 14  wherein the communication includes a command and write data.  
   
   
       16 . The method as recited in  claim 11 , further comprising: 
 receiving a calibration clock on the terminal in the first mode of operation; and    distinguishing between the calibration clock and serial communications in control logic coupled to the terminal.    
   
   
       17 . The method as recited in claim as recited in  claim 11  further comprising controlling one or more clock outputs according to the voltage value of the terminal in the second mode of operation.  
   
   
       18 . The method as recited in  claim 11  wherein the terminal is on a package, the package including an integrated circuit and a resonating device, the resonating device being one of a crystal and surface acoustic wave (SAW) device.  
   
   
       19 . An apparatus comprising: 
 a terminal; and    means for permanently converting the terminal from a first mode of operation in which serial communications are received over the terminal into a second mode of operation in which the terminal functions as a control input to selectively enable an output according to a voltage value on the terminal.    
   
   
       20 . The apparatus as recited in  claim 1 , further comprising a non-volatile memory for storing a terminal configuration determining the mode of operation of the terminal.  
   
   
       21 . The apparatus as recited in  claim 1  wherein the means for permanently converting is responsive to a communication received over the terminal to convert terminal to the second dedicated mode of operation.